The molecular genetics of variants and deficiencies of the human complement system will be studies using modern biochemical immunogenetic cytological and tissue culture methods. The program will be divided into four distinct projects: 1. The molecular basis of genetic polymorphism of complement proteins, 2. Chromosomal localization and expression of human complement genes, 3. Cellular and biochemical studies of human complement deficiencies, and 4. Development of biochemical methods for studies of the molecular pathobiology of complement deficiencies in animal models.